Geothermal Energy and Hydropower: Comprehensive Study Notes

Geothermal Energy

  • Definition: Geothermal energy is heat from within the Earth used for heating, electricity generation, and other energy conversion processes.
  • Etymology: The word geothermal comes from the Greek words "geo" (earth) and "therme" (heat).
  • Why renewable: Heat is continuously produced inside the Earth (radioactive decay in rocks).
  • Forms of use: Bathing, heating buildings, generating electricity, and other energy conversion processes.
  • Origin of geothermal energy: Deep inside the Earth, from the slow decay of radioactive particles in the Earth's core (a process that happens in all rocks).

2 TYPES OF ENERGY RESOURCES

  • GEOTHERMAL ENERGY
  • HYDROPOWER ENERGY

TYPES OF GEOTHERMAL POWER PLANTSS

  • Dry Steam Plants
    • Process: Direct use of naturally occurring underground steam to drive a turbine connected to a generator.
    • Typical flow: Production well -> turbine -> generator; steam condenses and is re-injected via an injection well.
    • Components often shown: Rock layers, production well, injection well, turbine, generator.
  • Flash Steam Plants
    • Process: Hot geothermal water (typically very hot) is brought to surface.
    • Mechanism: Pressure drop causes some of the hot water to flash into steam, which drives a turbine.
    • Additional equipment: Flash tank, turbine, generator; rock layers; production and injection wells.
  • Binary Cycle Plants
    • Process: Closed-loop system using a secondary, low-boiling-point working fluid.
    • Mechanism: Heat from geothermal reservoir transfers to the working fluid via a heat exchanger, driving a turbine without using reservoir steam.
    • Key components: Heat exchanger, working fluid, turbine, generator; rock layers; production and injection wells.

A DRY STEAM GEOTHERMAL POWER PLANT IS A TYPE OF GEOTHERMAL POWER PLANT

  • Directly utilizes underground steam to generate electricity.
  • Steam is extracted via wells, channeled to turbines, and used to drive generators.
  • Result: Electricity generation.

A FLASH STEAM GEOTHERMAL POWER PLANT

  • Uses high-temperature geothermal water (typically T > 360^\circ F or 182^\circ C).
  • Process: Hot water reaches surface; rapid pressure drop causes some water to flash into steam to drive a turbine.
  • Output: Electricity via turbine and generator.

A BINARY CYCLE POWER PLANT

  • Closed-loop system using a secondary working fluid with a low boiling point.
  • Heat from geothermal reservoir transfers to the working fluid via a heat exchanger.
  • The working fluid drives a turbine and generator.
  • Key components: Heat exchanger, working fluid, turbine, generator; rock layers; production and injection wells.

SOURCES OF GEOTHERMAL ENERGY

  • HYDROTHERMAL SYSTEMS: Hot water or steam near the Earth’s surface.
  • MAGMA AND HOT DRY ROCK: Deep magma and hot rocks; Enhanced Geothermal Systems (EGS) use drilling and water injection to create steam.
  • OLD MINESHAFTS AND CANALS: Existing infrastructures repurposed for direct heating or shallow geothermal applications.
  • TECTONIC PLATE BOUNDARIES: Reservoirs commonly found where tectonic activity (volcanic/seismic) is prevalent.
  • Example: Leyte Geothermal Plant, Philippines.

1. HYDROTHERMAL SYSTEMS

  • Characteristics: Hot water or steam near the surface; accessible for direct use or electricity generation.
  • Examples: Hot springs, geysers, fumaroles.

2. MAGMA AND HOT DRY ROCK

  • Magma: Molten rock deep underground; very high temperatures but challenging to access.
  • Hot dry rock: Crustal rocks heated by magma or radioactive decay; can be heated by proximity to magma.
  • Enhanced Geothermal Systems (EGS): Drilling to create a reservoir, injecting water to create steam.
  • Typical schematic elements: Insulating rock layers, injection well, production well, heat exchanger, turbine, generator, cooling tower, geothermal reservoir, depth measurements.

3. OLD MINESHAFTS AND CANALS

  • adaptation: Old mines and canals can be converted into boiler rooms or heat extraction sites for direct heating or shallow geothermal use.
  • Infrastructure transformation: Old vertical shafts repurposed for geothermal heat exchange.

4. TECTONIC PLATE BOUNDARIES

  • Geothermal reservoirs are most prevalent along plate boundaries due to volcanic and seismic activity.
  • Result: Higher opportunities for geothermal energy exploitation.

GEOTHERMAL ENERGY IN PRACTICE

  • Geothermal energy has diverse uses including electricity generation, heating/cooling of buildings, agriculture, aquaculture, and various industrial applications.
  • Example plant: Leyte Geothermal Plant, Philippines.
  • Environmental/Practical implications:
    • Renewable and low-emission energy source.
    • Requires careful management of wells to avoid groundwater contamination and to sustain reservoir pressure.

USES OF GEOTHERMAL ENERGY

  • HEATING AND COOLING OF BUILDINGS
    • How it works: Geothermal heat pumps exploit relatively constant near-surface ground temperatures to heat in winter and cool in summer.
    • Applications: Homes, schools, malls, offices; district heating/cooling systems in cities.
    • Benefits: Up to 70\% reduction in heating/cooling bills; year-round operation with minimal maintenance; reduces greenhouse gas emissions.
  • AGRICULTURE
    • Use: Geothermal heat maintains warm, stable greenhouse environments, especially in cold regions.
    • Mechanism: Geothermal wells or surface heat exchange systems heat radiators or underfloor heating in greenhouses.
    • Benefits: Increases plant growth and yield; saves fuel; enables farming in cold climates.
    • Global examples: Netherlands and Turkey for vegetables and flowers.
  • AQUACULTURE
    • Use: Geothermal water warms fish tanks or ponds to optimal species temperatures (e.g., tilapia, catfish, shrimp).
    • Methods: Direct use of geothermal water or heat exchangers to transfer heat to fish tanks.
    • Benefits: Year-round farming; faster fish growth; reduces diseases caused by cold water.
    • Examples: Geothermal-assisted fish farming in the Philippines and New Zealand trout hatcheries.
  • INDUSTRIAL APPLICATIONS
    • Uses: Geothermal heat in dehydrators, ovens, dryers, sterilizers, etc.
    • Methods: Steam or hot water from geothermal reservoirs used directly or via heat exchangers.
    • Benefits: Reduces fuel and electricity costs; eco-friendly heat source; lowers carbon footprint.
  • SPECIFIC EXAMPLES OF INDUSTRIAL USES
    • Drying crops (fruits, herbs, grains)
    • Sterilizing food containers or packaging
    • Pasteurizing milk
    • Processing sugar or cheese
    • Various recipes and dishes listed in the source material illustrate practical culinary contexts.

HYDROPOWER / HYDROELECTRICITY

  • INTRODUCTION
    • Hydroelectricity is the process of converting mechanical energy from moving water into electrical energy.
    • It uses the energy of running water to drive turbines connected to generators.
    • It is a renewable energy source that contributes significantly to many national grids.

TYPES OF HYDROPOWER / HYDROELECTRICITY

  • IMPOUNDMENT FACILITIES (Dams)
    • Uses a dam to create a large reservoir.
    • Electricity generated when water passes through turbines in the dam.
    • Typical components: reservoir, dam, spillway, penstock, turbine, generator, transformers, transmission lines.
  • PUMPED STORAGE FACILITIES
    • Have a second reservoir below the dam.
    • Water is pumped from the lower to the upper reservoir to store energy for later release.
    • Key elements: upper reservoir, lower reservoir, penstock/tunnel, powerhouse, turbine/pump, generator.
  • RUN-OF-RIVER FACILITIES
    • Rely on natural water flow rather than large storage reservoirs.
    • Divert part of river water through turbines; may not require a dam.
    • Typical layout: channel, forebay, transmission interconnect, intake, powerhouse, turbine, generator, river tailrace.

SOURCES OF HYDROPOWER HYDROELECTRICITY

  • RIVERS AND STREAMS: Main source where dams and reservoirs regulate flow.
  • RAINFALL: Replenishes rivers, lakes, and reservoirs feeding hydro plants.
  • LAKES AND RESERVOIRS: Stored water behind dams is released to generate electricity.
  • TIDAL ENERGY: Some plants use tidal movements for power generation.
  • SNOWMELT: Melting snow from mountains contributes to river flow, especially in warmer seasons.

USES OF HYDROPOWER / HYDROELECTRICITY

  • ELECTRICITY GENERATION
    • Water flows through turbines in a dam, spinning them to activate generators.
    • Examples: Hydroelectric dams, run-of-river plants.
    • Benefits: Renewable and clean; reduces dependence on fossil fuels; provides reliable base-load power.
  • IRRIGATION SUPPORT
    • Dams store and release water for farmland.
    • Examples: Reservoirs supplying irrigation canals; dams supporting agricultural fields.
    • Benefits: Boosts crop production; reduces dependence on unpredictable rainfall; enhances food security.
  • WATER SUPPLY & DRINKING WATER SYSTEMS
    • Reservoirs store freshwater treated and supplied to households and industries.
    • Benefits: Provides clean drinking water; ensures year-round availability; supports urban and industrial growth.
  • FLOOD CONTROL & WATER MANAGEMENT
    • Dams regulate river flow by holding excess water during heavy rains and releasing it gradually.
    • Benefits: Protects communities; preserves ecosystems by maintaining steady flow; prevents property and crop damage.
  • RECREATIONAL & ECONOMIC ACTIVITIES
    • Reservoirs and dam sites support boating, fishing, tourism, and local economies.
    • Benefits: Provides economic activity; fosters tourism; supports communities during floods and droughts.

SUMMARY REMARKS

  • Geothermal and hydro resources provide diverse pathways to renewable energy, combining direct heating, electricity generation, and support for water systems.
  • They offer environmental benefits, including reduced greenhouse gas emissions and decreased fossil fuel dependence, but require careful management of resources and infrastructure.
  • The content emphasizes real-world examples (Leyte Geothermal Plant; Netherlands/Turkey greenhouse use; New Zealand trout hatcheries) and practical applications across residential, agricultural, and industrial sectors.
  • Equations and thresholds: notable numerical reference for geothermal temperature threshold in flash steam plants is 360^\circ F or 182^\circ C.
  • Notable benefits across both domains include cost reductions (e.g., up to 70\% in heating/cooling costs) and reliable base-load electricity for grids.